,PE Mechanical – Thermal and Fluids Systems Questions, Correct
Answers, and Detailed Explanations for Students||Already Graded A+
Question 1
A pump delivers water at a flow rate of 500 gallons per minute (gpm)
against a total dynamic head of 120 ft. Which parameter is used to
determine the hydraulic power required?
A. Water density only
B. Flow rate and total dynamic head
C. Pipe diameter only
D. Fluid viscosity only
Correct Answer: B. Flow rate and total dynamic head
Explanation:
Hydraulic power is determined by the product of the flow rate and the
total dynamic head, adjusted for the fluid's specific weight and pump
efficiency.
Question 2
According to the First Law of Thermodynamics, energy in a closed
system:
A. Is continuously created
B. Is continuously destroyed
C. Can neither be created nor destroyed, only transformed
D. Always increases during a process
Correct Answer: C. Can neither be created nor destroyed, only
transformed
,Explanation:
The First Law of Thermodynamics states that energy is conserved. It
may change forms, such as from heat to work, but the total energy
remains constant.
Question 3
Which dimensionless number represents the ratio of inertial forces to
viscous forces in fluid flow?
A. Prandtl Number
B. Reynolds Number
C. Mach Number
D. Nusselt Number
Correct Answer: B. Reynolds Number
Explanation:
The Reynolds number predicts whether flow is laminar or turbulent by
comparing inertial and viscous forces.
Question 4
In a steady-flow nozzle, the primary purpose is to:
A. Increase pressure
B. Increase fluid velocity
C. Reduce temperature
D. Increase density
Correct Answer: B. Increase fluid velocity
, Explanation:
A nozzle converts pressure energy into kinetic energy, producing high
fluid velocity.
Question 5
Which heat transfer mechanism occurs through electromagnetic
waves?
A. Conduction
B. Convection
C. Radiation
D. Diffusion
Correct Answer: C. Radiation
Explanation:
Radiation transfers heat without requiring a physical medium and
occurs through electromagnetic waves.
Question 6
The efficiency of a Carnot heat engine depends primarily on:
A. Working fluid
B. Compressor size
C. Temperatures of the heat source and sink
D. Pump efficiency
Correct Answer: C. Temperatures of the heat source and sink
Answers, and Detailed Explanations for Students||Already Graded A+
Question 1
A pump delivers water at a flow rate of 500 gallons per minute (gpm)
against a total dynamic head of 120 ft. Which parameter is used to
determine the hydraulic power required?
A. Water density only
B. Flow rate and total dynamic head
C. Pipe diameter only
D. Fluid viscosity only
Correct Answer: B. Flow rate and total dynamic head
Explanation:
Hydraulic power is determined by the product of the flow rate and the
total dynamic head, adjusted for the fluid's specific weight and pump
efficiency.
Question 2
According to the First Law of Thermodynamics, energy in a closed
system:
A. Is continuously created
B. Is continuously destroyed
C. Can neither be created nor destroyed, only transformed
D. Always increases during a process
Correct Answer: C. Can neither be created nor destroyed, only
transformed
,Explanation:
The First Law of Thermodynamics states that energy is conserved. It
may change forms, such as from heat to work, but the total energy
remains constant.
Question 3
Which dimensionless number represents the ratio of inertial forces to
viscous forces in fluid flow?
A. Prandtl Number
B. Reynolds Number
C. Mach Number
D. Nusselt Number
Correct Answer: B. Reynolds Number
Explanation:
The Reynolds number predicts whether flow is laminar or turbulent by
comparing inertial and viscous forces.
Question 4
In a steady-flow nozzle, the primary purpose is to:
A. Increase pressure
B. Increase fluid velocity
C. Reduce temperature
D. Increase density
Correct Answer: B. Increase fluid velocity
, Explanation:
A nozzle converts pressure energy into kinetic energy, producing high
fluid velocity.
Question 5
Which heat transfer mechanism occurs through electromagnetic
waves?
A. Conduction
B. Convection
C. Radiation
D. Diffusion
Correct Answer: C. Radiation
Explanation:
Radiation transfers heat without requiring a physical medium and
occurs through electromagnetic waves.
Question 6
The efficiency of a Carnot heat engine depends primarily on:
A. Working fluid
B. Compressor size
C. Temperatures of the heat source and sink
D. Pump efficiency
Correct Answer: C. Temperatures of the heat source and sink
